Driving circuit of a lamp and method for operating the driving circuit of the lamp

Abstract

A driving circuit and a method for operating the driving circuit is provided for a lamp, the lamp includes a lighting unit, and a first and a second pair of connection pins for coupling the driving circuit to a power supply unit. The driving circuit includes a pre-heating detection circuit and a protection circuit. The pre-heating detection circuit is coupled to the first pair of connection pins and configured to detect a voltage between the first pair of connection pins and output a reference voltage. The protection circuit includes a switching circuit connected in series with the lighting unit, the protection circuit is configured to compare the reference voltage with an input voltage of the lamp and turn on the switching circuit to light the lighting unit when the input voltage of the lamp is greater than the reference voltage.

The invention claimed is: 
     
       1. A driving circuit of a lamp for preventing an electric shock during installation or removal, the lamp comprising a lighting unit, and a first and a second pair of connection pins for coupling the driving circuit to a power supply unit, the driving circuit comprising:
 a pre-heating detection circuit coupled to the first pair of connection pins, the pre-heating detection circuit comprising an optocoupler and configured to detect a pre-heating voltage between the first pair of connection pins and to output a reference voltage via the optocoupler; and 
 a protection circuit comprising a switching circuit connected in series with the lighting unit and operably connected to the optocoupler, the protection circuit configured to compare the reference voltage output from the optocoupler with an input voltage of the lamp and turn off the switching circuit thereby turning off the power supply to the lighting unit when the input voltage of the lamp is less than the reference voltage. 
 
     
     
       2. The driving circuit according to  claim 1 , wherein the protection circuit further comprises a control circuit operably coupled to the pre-heating detection circuit to receive the reference voltage from the optocoupler, wherein the control circuit is configured to output a control signal to the switching circuit via a comparative result between the reference voltage and the input voltage of the lamp. 
     
     
       3. The driving circuit according to  claim 2 , wherein when the input voltage of the lamp is greater than the reference voltage, the control circuit outputs a first control signal to the switching circuit to turn on the switching circuit. 
     
     
       4. The driving circuit according to  claim 1 , wherein the optocoupler of the pre-heating detection circuit outputs a first reference voltage when the voltage between the first pair of connection pins is less than 2 volts, and wherein the optocoupler of the pre-heating detection circuit outputs a second reference voltage when the voltage between the first pair of connection pins is greater than or equal to 2 volts, wherein the first reference voltage is greater than the second reference voltage. 
     
     
       5. The driving circuit according to  claim 4 , wherein a voltage value of the first reference voltage is greater than or equal to 300 volts, and a voltage value of the second reference voltage is from 200 volts to 270 volts. 
     
     
       6. The driving circuit according to  claim 1 , further comprising an additional pre-heating detection circuit coupled to the second pair of connection pins of the lamp, the additional pre-heating detection circuit comprising a second optocoupler and configured to detect a pre-heating voltage between the second pair of connection pins and output the pre-heating reference voltage via the second optocoupler together with the pre-heating detection circuit, and wherein the pre-heating detection circuit is connected in series with the additional pre-heating detection circuit. 
     
     
       7. The driving circuit according to  claim 6 , wherein the pre-heating detection circuit and the additional pre-heating detection circuit output a third reference voltage when at least one of the voltage between the first pair of connection pins and the voltage between the second pair of connection pins is less than 2 volts, the pre-heating detection circuit and the additional pre-heating detection circuit output a fourth reference voltage when both the voltage between the first pair of connection pins and the voltage between the second pair of connection pins are greater than or equal to 2 volts, wherein the third reference voltage is greater than the fourth reference voltage. 
     
     
       8. The driving circuit according to  claim 7 , wherein a voltage value of the third reference voltage is greater than or equal to 300 volts, and a voltage value of the fourth reference voltage is less than 300 volts. 
     
     
       9. The driving circuit according to  claim 1 , further comprising a first impedance circuit coupled to the first pair of connection pins and configured to receive an alternating voltage from the first pair of connection pins and provide a rectified input voltage. 
     
     
       10. The driving circuit according to  claim 9 , wherein the input voltage of the lamp is selected from the alternating voltage and the rectified input voltage. 
     
     
       11. The driving circuit according to  claim 1 , wherein the switching circuit comprises an initial starting current-limiting circuit configured to limit a current through the lighting unit. 
     
     
       12. A method for operating a driving circuit of a lamp to prevent an electric shock during installation or removal of the lamp, the lamp comprising a lighting unit, and a first pair of connection pins and a second pair of connection pins for coupling the driving circuit to a power supply unit, the method comprising:
 detecting, by a pre-heating detection circuit of the driving circuit, a voltage between the first pair of connection pins; 
 outputting, by an optocoupler of the pre-heating detection circuit of the driving circuit, a reference voltage based on the voltage between the first pair of connection pins; 
 comparing, by a protection circuit of the driving circuit, the reference voltage received from the optocoupler with an input voltage of the lamp; and 
 controlling, by the protection circuit, the lighting unit to be turned on when the reference voltage is greater than the input voltage or to be turned off when the reference voltage is less than the input voltage.